Virial third

Equation (10a) is somewhat inconvenient first, because we prefer to use pressure rather than volume as our independent variable, and second, because little is known about third virial coefficients It is therefore more practical to substitute... 

Equations (7b) and (8) into Equation (6), neglecting all third virial coefficients. We then obtain... 

Stigter and Dill [98] studied phospholipid monolayers at the n-heptane-water interface and were able to treat the second and third virial coefficients (see Eq. XV-1) in terms of electrostatic, including dipole, interactions. At higher film pressures, Pethica and co-workers [99] observed quasi-first-order phase transitions, that is, a much flatter plateau region than shown in Fig. XV-6. 

The third virial coefficient C(7) depends upon tliree-body interactions, both additive and non-additive. The relationship is well understood [106. 107. 111]. If the pair potential is known precisely, then C(7) ought to serve as a good probe of the non-additive, tliree-body interaction energy. The importance of the non-additive contribution has been confimied by C(7) measurements. Unfortunately, large experimental uncertainties in C (7) have precluded unequivocal tests of details of the non-additive, tliree-body interaction. 

The nth virial coefficient can be written as sums of products of Mayer/-fiinctions integrated over the coordinates and orientations of n particles. The third virial coefficient for spherically syimnetric potentials is... 

This leads to the third virial coefficient for hard spheres. In general, the nth virial coefficient of pairwise additive potentials is related to the coefficient7) in the expansion of g(r), except for Coulombic systems for which the virial coefficients diverge and special teclmiques are necessary to resiim the series. 

Similarly, the third virial coefficients are defined by equation 26 ... 

Because virial coefficients beyond the third are rarely available, equations 23 and 30 are usually tmncated after two or three terms. For low pressures, the two-term tmncation of equation 30 is preferred ... 

The acentric factor, CO, was the third parameter used (20) in an equation based on the second virial coefficient. This equation was further modified and is suitable for reduced temperatures above 0.5. 

Miscellaneous Generalized Correlations. Generalized charts and corresponding states equations have been pubhshed for many other properties in addition to those presented. Most produce accurate results over a wide range of conditions. Some of these properties include (/) transport properties (64,91) (2) second virial coefficients (80,92) (J) third virial coefficients (72) (4) Hquid mixture activity coefficients (93) (5) Henry s constant (94) and 6) diffusivity (95). 

The coefficient Bij characterizes a bimolecular interaction between molecules i and J, and therefore Bij = Bji. Two lands of second virial coefficient arise Bn and By, wherein the subscripts are the same (i =j) and Bij, wherein they are different (i j). The first is a virial coefficient for a pure species the second is a mixture property, called a cross coefficient. Similarly for the third virial coefficients Cm, Cjjj, and are for the pure species and Qy = Cyi = Cjn, and so on, are cross coefficients. 

Motivated by a puzzling shape of the coexistence line, Kierlik et al. [27] have investigated the model with Lennard-Jones attractive forces between fluid particles as well as matrix particles and have shown that the mean spherical approximation (MSA) for the ROZ equations provides a qualitatively similar behavior to the MFA for adsorption isotherms. It has been shown, however, that the optimized random phase (ORPA) approximation (the MSA represents a particular case of this theory), if supplemented by the contribution of the second and third virial coefficients, yields a peculiar coexistence curve. It exhibits much more similarity to trends observed in... 

When the virial expansion (truncated after the third term) is substituted into Eq. (6), we obtain... 

The next level of approximation is valid to higher pressures. It assumes that the gas mixture obeys the virial equation of state, with the third, fourth and higher, virial coefficients equal to zero. Thus... 

Figure A3.1 Examples of (a) the second virial coefficient and (b) the third virial coefficient [from equation (A3.3)] as a function of temperature for several gases.

If p is not high, terms beyond the second and third virial coefficients in equation (A3.3) and (A3.5) are usually small and can be neglected. This is fortunate, since experimental data are usually not accurate enough to give reliable values for the higher order terms. At low pressures, equation (A3.5) is often used and truncated after the second virial coefficient so that... 

This expression is called the virial equation. The coefficients B, C,. . . are called the second virial coefficient, third virial coefficient, and so on. The virial coefficients, which depend on the temperature, are found by fitting experimental data to the virial equation. 

In some extreme cases, third or even higher virial coefficient(s) may be necessary to adequately represent the data for example /c-carrageenan [90] and alginate [91]. In a further study on alginates, Straatman and Bor-chard [92] demonstrated excellent agreement between and B values ob-... 

The experimental second and third virial coefficients for steam are however widely available. But these experimental quantities should be used with more care than has been usual in the past. The prevailing notion asserts that a good two-body potential should yield the second virial in full agreement with the exper-... 

In Figure 1 we show the computed and the experimental second virial for the two potentials obtained in Ref. 26, for the most widely used semi-empirical ST2 potential, and for the Hartree-Fock potential. For the third virial coefficient we refer elsewhere. ... 

Factor relating the third virial coefficient Tz to Vl (Chaps. VII and XII). 

A3 AIBN c Cp DLS DLVO DSC EO GMA HS-DSC KPS LCST Osmotic third virial coefficient 2,2 -Azobis(isobutyronitrile) Polymer concentration Partial heat capacity Dynamic light scattering Derjaguin-Landau-Verwey-Overbeek Differential scanning calorimetry Ethylene oxide Glycidylmethacrylate High-sensitivity differential scanning calorimetry Potassium persulphate Lower critical solution temperature... 

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